It’s hard to believe now, but Copernicus worked out that the Earth revolves around the sun decades before scientists figured out that blood circulates through the human body. An English physician, William Harvey, announced in 1628 that the heart pumps blood through the arteries and veins, only to be denounced for decades by conservative doctors. It was against this backdrop in 1665 — a time when pocket sundials were all the rage — that the first blood transfusions were carried out.